1. Field of the Invention
This invention relates to an air intake and a method for breathing air using the air intake which are preferably employed in aerospace industry.
2. Description of the Related Art
An air intake is an important constituent element to affect on the engine performance of a supersonic air-breathing engine or the like because the air intake deaccelerates and compresses the air inflow introduced therein. The air intake can be classified as an internal compression type air intake, an external compression type air intake or a mixed compression type air intake. Particularly, the mixed compression type air intake is balanced because the air intake can exhibit intermediate features, in comparison with the internal compression type air intake and the external compression type air intake.
FIG. 1 is a cross sectional view schematically illustrating the structure of a conventional mixed compression type air intake, and FIG. 2 is an enlarged perspective view illustrating the forefront of the air intake illustrated in FIG. 1. As is apparent from FIGS. 1 and 2, the air intake 10 includes a center structural body 11 called as a “spike” and a cowl 12 provided so as to enclose the rear portion of the spike 11 via a space 13. The spike 11 is formed axial symmetrically, and has a porous wall 14 at the side thereof.
If the air intake 10 is installed in a supersonic air breathing engine, it can generate a shock wave from an air inflow introduced therein through the impact with the forefront 11A of the spike 11. In this case, the air inflow is partially leaked as a spillage flow outside from the space 13 formed by the spike 11 and the cowl 12, so that the capture flow ratio of the air inflow may be decreased. Since the shock wave tends to be receded from the cowl rip 12A as the velocity of the air inflow is decreased, the capture flow ratio of the air inflow is also decreased when the velocity of the air inflow is decreased below the designed velocity range of air inflow of the air intake 10.
Moreover, the shock wave is introduced directly into the space 13 as the velocity of the air inflow is increased, generating a flow field with a strong inversive pressure gradient in the air intake 10. In this case, a boundary layer, which is composed of a flow flux with a relatively low flow velocity and formed nearby the inner walls of the spike 11 and the cowl 12, may be destroyed, and the air flow may be shut off from the air intake 10. As a result, it may be that the air intake 10 can not be started. In this point of view, with the air intake 10 illustrated in FIGS. 1 and 2, since the porous wall 14 is partially provided at the side of the spike 11, the boundary layer is released into an air bleeding path 15 via the porous wall 14, and then, released outside from the air intake 10 through the air bleeding path 15. In this case, however, since the air inflow is partially released outside from the air intake 10, in consequence, the capture flow ratio of the air inflow is decreased.